Multiple forms of cytochrome P450, the terminal oxidase of a mixed- function oxidase responsible for the metabolism of steroids, fatty acids, heme and xenobiotics, exist in rat liver microsomes. Each form will be purified and characterized in order to determine the molecular basis for their differences. The hemoproteins will be analyzed for amino acid and carbohydrate composition. Studies to determine the amino acid sequence will then be initiated. Antibodies to the various hemoproteins will be used to further compare the hemoproteins and to determine which enzymatic activities they catalyze.